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. 2026 Apr 15;88(5):2888–2896. doi: 10.1097/MS9.0000000000004872

Analyzing the effects of anemia on the outcomes of mechanical thrombectomy in ischemic stroke patients: a systematic review and meta-analysis

Mostafa Hossam El Din Moawad a,b, Ibrahim Serag c, Ibraheem M Alkhawaldeh d, Ahmed F Gadelmawla e,f, Mohammed Khaled Mohammed g, Mohamed Samir A Zaki h, Hamza A Abdul-Hafez i,*, Mohamed Abouzid j
PMCID: PMC13132313  PMID: 42078595

Abstract

Background:

Anemia is a common yet often overlooked condition in patients with acute ischemic stroke (AIS) undergoing mechanical thrombectomy. Hemoglobin levels play a crucial role in oxygen transport, and their depletion may exacerbate ischemic injury and worsen functional outcomes. This meta-analysis aimed to evaluate the effect of anemia on the functional and survival outcomes of patients with AIS treated with mechanical thrombectomy.

Methods:

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we searched electronic databases (PubMed, Scopus, and Web of Science) to identify eligible studies reported up to January 2025. Using Review Manager software, we reported outcomes as odds ratios (ORs) or mean difference and confidence intervals (CIs). A P-value ≤ 0.05 was considered statistically significant.

Results:

Nine retrospective cohort studies comprising 2189 patients were included. Anemia was significantly associated with lower odds of achieving good functional outcomes (OR = 0.30, 95% CI: 0.13–0.68, P = 0.004) and a higher risk of mortality (OR = 1.76, 95% CI: 1.19–2.60, P = 0.005). No significant association was found between anemia and symptomatic intracerebral hemorrhage risk (OR = 0.95, 95% CI: 0.34–2.27, P = 0.91). Younger age, lower baseline NIH Stroke Scale, and higher hemoglobin levels were significant predictors of good prognosis.

Conclusion:

Anemia negatively impacted functional recovery and survival in patients with AIS undergoing mechanical thrombectomy. Given these findings, optimizing hemoglobin levels may be a potential strategy to improve patient outcomes. Further prospective studies are needed to explore the benefits of anemia correction strategies in stroke management.

Keywords: anemia, good functional outcomes, hemoglobin, ischemic stroke, mechanical thrombectomy

Introduction

Acute ischemic stroke (AIS) is a significant contributor to mortality and disability globally[1]. The administration of AIS has traditionally been predominantly supportive. In the past 25 years, two significant advancements in treating AIS have emerged. In 1996, the Food and Drug Administration approved intravenous tissue-type plasminogen activator (tPA) to treat AIS, significantly transforming AIS management[2,3]. Nonetheless, numerous patients were ineligible for tPA due to delayed presentation, age, and comorbidities, resulting in an unmet demand for effective recanalization in individuals with massive artery occlusions. Endovascular stroke therapy (mechanical thrombectomy) utilizing thrombus retrievers was established to fulfill those unfulfilled requirements[4].

AIS represents a significant global health challenge leading to neuronal injury and long-term functional impairment. Current therapeutic approaches primarily focus on restoring cerebral blood flow; however, they often fall short of preventing secondary neuronal damage and promoting neurological recovery. This limitation has prompted increasing interest in adjunctive strategies that may mitigate ischemia-related injury and improve outcomes[5].

Various patient comorbidities can influence the clinical outcomes of mechanical thrombectomy. Anemia, primarily caused by iron deficiency, has been identified as a potentially modifiable factor associated with increased morbidity and mortality in AIS patients, particularly those with large vessel occlusion, who are primarily treated with mechanical thrombectomy. Although anemia is not traditionally recognized as a risk factor for ischemic stroke, it is increasingly considered an additional modifiable factor. Recently, numerous studies have investigated its potential impact on AIS outcomes. Anemia is observed in approximately 25% of patients with AIS upon admission[6]. Studies have identified anemia as an independent predictor of poor clinical outcomes in patients treated with intravenous thrombolysis, mechanical thrombectomy, or a combination of both[7–11]. However, some studies have failed to find a clear association, indicating the need for further research[12–14].

Maintaining normal hemoglobin and hematocrit levels is critical for ensuring adequate oxygen delivery to cerebral tissue. This is especially important in ischemic stroke patients, where oxygen supply is vital to meet the increased metabolic demands of penumbral tissue. While cerebral autoregulation can compensate for anemia in healthy individuals with hemoglobin levels as low as 8 g/dL, severe anemia (hemoglobin levels between 5 and 7 g/dL) significantly reduces oxygen transport capacity due to insufficient cerebral vasodilation. Furthermore, anemia can induce the release of pro-inflammatory cytokines such as interleukin-6 and tumor necrosis factor-α, potentially exacerbating ischemic injury[14,15].

Managing anemia during the peri-procedural period in patients undergoing mechanical thrombectomy is a critical area of focus, with prevention being critical. Aspiring blood during thrombectomy can contribute to postoperative reductions in hemoglobin levels. While a greater number of device passes may further decrease hemoglobin levels, the precise relationship between procedural details and the development of postoperative anemia remains unclear[6].

Current guidelines have yet to address the risk of anemia in patients with AIS undergoing mechanical thrombectomy and its association with worse prognosis to discuss further the optimal management and preventive strategies[16,17]. Therefore, we conducted the present systematic review and meta-analysis to explore the effect of hemoglobin concentration and anemia among ischemic stroke patients undergoing mechanical thrombectomy on the prognosis of these patients and to identify the predictors of this prognosis.

Methods

This systematic review and meta-analysis was carried out in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement[18] and the Cochrane Handbook for Systematic Reviews of Interventions[19].

Searching process

A comprehensive literature search was conducted in PubMed/MEDLINE, Scopus, and Web of Science from database inception to January 2025. The search strategy combined Medical Subject Headings terms and free-text keywords, including: (“acute ischemic stroke” OR “ischemic stroke” OR “stroke”) AND (“mechanical thrombectomy” OR “endovascular therapy” OR “EVT” OR “MT” OR “thrombectomy”) AND (“anemia” OR “hemoglobin”). Searches were conducted utilizing the title and abstract on PubMed, keywords, title, and abstract on Scopus, and the abstract on Web of Science. No restrictions on language or countries was applied. The articles obtained from the search method were imported into EndNote to eliminate duplicates prior to initiating the screening process[20]. Reference lists of included studies were also manually screened to identify additional eligible articles.

HIGHLIGHTS

  • Anemia is significantly associated with worse functional outcomes (lower modified Rankin score 0–2 rates) and higher mortality.

  • No significant link between anemia and symptomatic intracerebral hemorrhage.

  • Predictors of good outcome: higher hemoglobin (mean difference 0.56 g/dL; OR per g/dL 1.23), younger age, and lower baseline National Institutes of Health Stroke Scale.

  • Multiple device passes during thrombectomy may contribute to anemia and worsen outcomes.

Eligibility criteria and screening

The articles obtained after the removal of duplicates were uploaded to Rayyan for screening[21]. PICO criteria were utilized during the screening process, which occurred in two phases: title and abstract, followed by full-text screening. The population (P) comprised patients with ischemic stroke and anemia, the intervention (I) was mechanical thrombectomy, the comparison (C) was patients without anemia, and the outcomes (O) included efficacy and safety parameters such as modified Rankin score (mRs), symptomatic intracerebral hemorrhage (sICH), and mortality. The study design encompassed randomized controlled trials and cohort studies. We excluded reviews, case reports, editorials, and unpublished data. We did not exclude studies based on quality assessment as this is a subjective procedure. The majority of studies applied the World Health Organization definition of anemia, namely hemoglobin levels <13 g/dL in men and <12 g/dL in women. A small number of studies used closely comparable hemoglobin thresholds or categorized anemia severity based on hemoglobin concentration ranges. Given the overall consistency of hemoglobin cutoffs across studies, variability in anemia definitions was considered minimal and unlikely to substantially affect the pooled estimates.

Data extraction

Using Microsoft Excel sheets, we conducted the process of data extraction from the included articles. We extracted the baseline and summary of the included studies, including study design, country, sample size, age, gender, and baseline National Institutes of Health Stroke Scale (NIHSS). Outcomes included events and a total of mRs 0–2, mRs 3–6, sICH, and mortality; mean and standard deviation of hemoglobin levels among good and bad outcomes; and odds ratio (OR) of predictors of good outcomes (mRs 0–2), such as age, hemoglobin levels, and baseline NIHSS.

Quality assessment

Two authors performed evaluations of quality and bias risk, resolving discrepancies through consensus or discussions with the senior author. The New Castle Ottawa Scale, which allocates a star rating from 0 to 9 for each study, was employed to evaluate the quality of observational cohort studies. Each question can receive a rating of one or zero stars, except for the comparison question, which may attain a maximum of two stars. A study rated 1–3 stars is deemed low quality; 4–6 stars indicate intermediate quality; and 7–9 stars signify high quality[22].

Statistical analysis

Statistical analysis was performed utilizing Review Manager software[23]. We computed the mean difference (MD) for continuous variables and OR for dichotomous variables by aggregating occurrences and totals, along with adjusted OR for predictors of favorable outcomes. We employed I2 to evaluate heterogeneity, categorizing 0%–30% as low heterogeneity, 30%–70% as moderate heterogeneity, and 70%–100% as high heterogeneity. A P-value of 0.05 was employed to evaluate the statistical significance of heterogeneity. We employed the random effects model for analyzing outcomes exhibiting substantial heterogeneity, while the fixed effects model was utilized for outcomes demonstrating non-significant heterogeneity.

Results

Literature search

  1. An electronic database search yielded 150 records, of which 67 were duplicates. The remaining 83 underwent title and abstract screening, excluding 68 records for not meeting the inclusion criteria. A full-text review was conducted on 15 articles, resulting in the selection of 9 studies that met the criteria for analysis[6,9,10,14,15,24–27]. (Fig. 1)

Figure 1.

Figure 1.

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PRISMA flow diagram of searching and screening.

Characteristics of the included studies

This meta-analysis included nine retrospective cohort studies comprising 2189 patients across Poland, Finland, the USA, Taiwan, Japan, China, the Netherlands, and Turkey. Sample sizes ranged from 40 to 361 patients, with varying distributions of anemic and non-anemic groups. The mean age of patients ranged from 60 to 80 years. Baseline NIHSS scores, where available, ranged from 12.9 to 19. A summary of characteristics can be found in Table 1.

Table 1.

Baseline characteristics of included studies.

Study ID Study design Country Sample size Age, mean ± SD Male, n (%) Baseline NIHSS (mean ± SD)
Anemia No anemia Anemia No anemia Anemia No anemia Anemia No anemia
Wrona 2024 Retrospective cohort Poland 157 74.5 ± 4.5 73 (46.4) 18 ± 1.75
Pienimäki 2020 Retrospective cohort Finland 285 68 ± 11 115 (40) 16.5 ± 7
Nisar 2023 Retrospective cohort USA 81 139 64.88 ± 16.15 63.65 ± 13.15 40 (49.38) 77 (55.40) 14.76 ± 5.65 14.99 ± 5.73
Nisar 2021 Retrospective cohort USA 67 121 60.28 ± 12.95 34 (33.66) 67 (66.35) 12.97 ± 5.14
Lin 2023 Retrospective cohort Taiwan 148 73.1 ± 12.7 68 (45.9) 17.6 ± 2
Inui 2023 Retrospective cohort study Japan 168 136 78.7 ± 8.97 80.33 ± 9.74 68 (50) 63 (38) 19 ± 3 18 ± 3.25
Feng 2023 Retrospective cohort China 310 72 ± 4.75 139 (44.8) 15 ± 2
Ceulemans 2024 Retrospective cohort Netherlands 126 361 76.67 ± 11.25 70.67 ± 13.4 70 (56) 186 (52) 15 ± 2 15 ± 2.25
Akpinar 2018 Retrospective cohort Turkey 40 50 63.3 ± 10.6 60 ± 12.3 16 27 13.9 ± 3.7 13.2 ± 4.2
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SD, standard deviation; NIHSS, National Institutes of Health Stroke Scale.

Quality assessment evaluation

Six studies were rated as high quality (total score from 7 to 9 stars), and three studies were rated as moderate quality (total score range from 5 to 6 stars; Table 2).

Table 2.

Quality assessment of cohort studies using the New Castle Ottawa Scale.

Study ID Selection (max 4) Comparability (max 2) Outcome (max 3) Total (max 9)
Wrona 2024 ☆☆☆ ☆☆ ☆☆☆ ☆☆☆☆☆☆☆☆
Pienimäki 2020 ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆
Nisar 2023 ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆
Nisar 2021 ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆
Lin 2023 ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆
Inui 2023 ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆
Feng 2023 ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆
Ceulemans 2024 ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆
Akpinar 2018 ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆ ☆
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Meta-analysis

Good functional outcome (mRS 0–2)

A total of five studies (N = 1008 patients) assessed the impact of anemia on achieving a good functional outcome (mRS 0–2). The pooled OR was 0.30 [95% confidence interval (CI): 0.13–0.68, P = 0.004] in favor of the anemia group, indicating that patients without anemia had significantly better functional outcomes. Heterogeneity was high (I2 = 88%), suggesting some study variability (Fig. 2).

Figure 2.

Figure 2.

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Analysis of odds ratio of mRs 0–2 (good functional outcome) between anemia and no anemia group.

Poor functional outcome (mRS 3–6)

Four studies (N = 1219 patients) evaluated the relationship between anemia and poor functional outcome (mRS 3–6). The pooled OR was 0.96 (95% CI: 0.40–2.30, P = 0.42), showing no significant difference between the anemia and non-anemia groups. Heterogeneity was high (I2 = 91%; Fig. 3).

Figure 3.

Figure 3.

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Analysis of odds ratio of mRs 3–6 (poor functional outcome) between anemia and no anemia group.

Symptomatic intracerebral hemorrhage

Two studies (N = 560 patients) assessed the risk of sICH in anemic versus non-anemic groups. The pooled OR was 0.95 (95% CI: 0.34–2.27, P = 0.91), indicating no significant association between anemia and sICH risk. Heterogeneity was null (I2 = 0%; Fig. 4).

Figure 4.

Figure 4.

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Analysis of the odds ratio of sICH between the anemia and no-anemia group.

Mortality

Three studies (N = 719 patients) reported mortality rates. The pooled OR was 1.76 (95% CI: 1.19–2.6, P = 0.005), indicating that anemia was significantly associated with increased mortality risk. Heterogeneity was non-significant (I2 = 45%, P = 0.16; Supplemental Digital Content Figure S1, available at: http://links.lww.com/MS9/B98).

Hemoglobin levels

The pooled analysis of four studies (N = 933 patients) revealed a significant difference in hemoglobin levels between patients with good (mRS 0–2) and poor (mRS 3–6) outcomes. The MD was 0.56 g/dL (95% CI: 0.29–0.83, P < 0.0001), suggesting that higher hemoglobin levels were significantly associated with improved functional outcomes. Heterogeneity was negligible (I2 = 0%; Supplemental Digital Content Figure S2, available at: http://links.lww.com/MS9/B98).

Age as a predictor of good prognosis

Three studies analyzed age as a predictor of good functional outcomes (mRS 0–2). The pooled OR was 0.96 (95% CI: 0.94–0.97, P < 0.00001), indicating that younger age was a significant predictor of favorable prognosis. There was no heterogeneity (I2 = 0%; Supplemental Digital Content Figure S3, available at: http://links.lww.com/MS9/B98).

Baseline NIHSS as a predictor of good prognosis

Four studies assessed baseline NIHSS as a predictor of good functional recovery (mRS 0–2). The pooled OR was 0.92 (95% CI: 0.88–0.96, P = 0.0002), confirming that lower NIHSS scores at baseline were significantly associated with better neurological outcomes. Heterogeneity was moderate (I2 = 69%; Supplemental Digital Content Figure S4, available at: http://links.lww.com/MS9/B98).

Hemoglobin concentration as a predictor of good prognosis

A total of five studies examined hemoglobin concentration as a predictor of functional outcome (mRS 0–2). The pooled OR was 1.23 (95% CI: 1.13–1.33, P < 0.00001), demonstrating that higher hemoglobin levels were significantly correlated with improved prognosis. No heterogeneity existed (I2 = 0%; Supplemental Digital Content Figure S5, available at: http://links.lww.com/MS9/B98).

Discussion

Summary of findings

The findings indicated that anemia was significantly associated with poorer functional outcomes. Patients without anemia had a significantly better chance of achieving a good functional outcome (mRS 0–2). Additionally, higher hemoglobin levels were linked to better functional outcomes. This association had negligible heterogeneity, reinforcing the reliability of this result. However, no significant difference was observed between anemic and non-anemic patients regarding poor functional outcomes (mRS 3–6). Similarly, anemia was not found to be associated with sICH.

On the other hand, mortality analysis revealed that anemia was significantly associated with an increased risk of death. Predictive factors for good prognosis were also analyzed. Younger age was a significant predictor of better functional outcomes. Likewise, a lower baseline NIHSS score was strongly associated with improved neurological recovery. Furthermore, higher hemoglobin concentration was also identified as a predictor of favorable prognosis. Therefore, anemia appears to negatively impact functional recovery and survival in stroke patients, while higher hemoglobin levels, younger age, and lower baseline NIHSS scores are associated with better outcomes. These findings highlight the potential importance of monitoring and managing hemoglobin levels in stroke patients to improve prognosis.

Relationship between anemia and AIS

Anemia is a common illness in AIS patients, with its etiology involving processes such as diminished oxygen-carrying capacity, inflammation, energy imbalance, and hypercoagulation[28]. Reduced hemoglobin levels indicate diminished oxygen transport capability, resulting in insufficient oxygen delivery and an energy deficit in the ischemic penumbra[16,29]. Furthermore, anemia might induce the release of inflammatory mediators such as tumor necrosis factor-α[30]. The significance of inflammatory responses in advancing AIS and their correlation with unfavorable outcomes has been extensively acknowledged[31–34]. Research has demonstrated that inadequate dietary status and compromised immune response may lead to a poorer outcome[35].

Additionally, anemic patients may exhibit hypercoagulability, hence elevating the risk of ischemic events. Research indicates that severe anemia significantly increases the risk of stent thrombosis[36], and reduced hemoglobin levels are a robust predictor of in-stent restenosis following percutaneous coronary intervention (PCI)[37]. Numerous studies have identified baseline hemoglobin as a crucial predictor of mortality and ischemia events in PCI[38,39]. A U-shaped correlation has been identified between hemoglobin levels and adverse prognosis, overall mortality, and stroke severity in ischemic stroke[28,40]. Additional studies indicated that diminished hemoglobin levels and variability were associated with death at three months in AIS patients receiving mechanical thrombectomy[9]. From a biological standpoint, anemia may adversely affect AIS outcomes through multiple interrelated mechanisms. Reduced hemoglobin concentration leads to impaired oxygen-carrying capacity, resulting in insufficient oxygen delivery to the ischemic penumbra, where neuronal tissue remains metabolically active yet vulnerable. This hypoxic environment exacerbates mitochondrial dysfunction, accelerates neuronal apoptosis, and limits the potential for tissue salvage. Moreover, anemia has been associated with heightened systemic and cerebral inflammatory responses, including increased levels of pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-6, which may amplify secondary neuronal injury. Additionally, anemia may contribute to hypercoagulability and endothelial dysfunction, thereby increasing the risk of microvascular thrombosis and infarct progression[16].

Relationship between mechanical thrombectomy and hemoglobin concentrations

Aspirational blood maneuvering with thrombi is crucial during mechanical thrombectomy, irrespective of the thrombectomy approach (e.g., stent retriever alone[41], contact aspiration technique[42], or combined technique[43,44]), potentially leading to reduced postoperative hemoglobin levels. While an increased number of device passes may lead to diminished postoperative hemoglobin levels, the correlation between the specifics of the mechanical thrombectomy process and postoperative anemia is still ambiguous. Inui et al[6] indicated that the moderate-to-severe anemia cohort experienced the most prolonged duration from groin puncture to initial successful recanalization, the longest interval from groin puncture to conclusive angiography, the greatest total number of device passes, the lowest incidence of first-pass effect, and the highest prevalence of perioperative subarachnoid hemorrhage. They established that hemoglobin concentrations following mechanical thrombectomy diminished as the number of device passes increased. In the multivariable analysis, moderate-to-severe anemia occurring within 24 hours post-mechanical thrombectomy was more prevalent in the cohort undergoing two device passes (adjusted OR, 3.45; 95% CI, 1.46–8.34), three device passes (adjusted OR, 7.21; 95% CI, 2.73–19.90), and four or more device passes (adjusted OR, 15.20; 95% CI, 6.07–41.10) compared to the cohort with one device pass[6].

This showed that increased device passes were associated with an increased risk of moderate-to-severe anemia due to the aspiration of blood with thrombi associated with a drop in hemoglobin concentration. Therefore, the sequence is increased aspiration during mechanical thrombectomy, followed by an increased drop in hemoglobin concentration, and worse outcomes follow this in ischemic stroke patients undergoing mechanical thrombectomy. A previous investigation indicated that a higher frequency of device passes correlated with infarct expansion, even among patients who experienced successful reperfusion[45]. A study indicated reduced hemoglobin levels upon admission correlated with infarct expansion[46]. Postoperative anemia resulting from several device passes may exacerbate infarct growth, leading to a diminished prognosis. Hemoglobin concentrations are pertinent in neurocritical care following mechanical thrombectomy, as a decrease in these levels correlates with diminished odds of a favorable outcome, even in patients attaining a final expanded Thrombolysis in Cerebral Infarction (eTICI) grade of 2c–3, as demonstrated by Inui et al[6] in their prior research.

Predictors of functional outcomes

Regarding the predictive variables of good prognosis, the current pooled analysis showed that better outcomes were associated with younger age, lower baseline NIHSS (lower rate of neurological dysfunction), and increased hemoglobin concentrations. Lin et al[24] revealed analogous results, indicating that post-mechanical thrombectomy patients who are younger and possess superior premorbid status exhibited functional independence in both short- and long-term outcomes, aligning with prior mechanical thrombectomy research[47]. Advanced age has been identified as a negative predictive indicator for functional outcomes in stroke patients undergoing mechanical thrombectomy in previous studies[48–50]. The diminished efficacy and elevated complication rates of mechanical thrombectomy may be potential explanations[51]. The correlation between premorbid function and functional outcomes post-stroke has been thoroughly examined in prior years[52,53]. Studies indicate that compromised premorbid condition is a significant predictor of unfavorable functional outcomes in survivors of mechanical thrombectomy[54]. A separate mechanical thrombectomy study indicated that a preadmission mRS of 0–2 serves as a predictive indicator for favorable outcomes at 90 days, following adjustments for age, medical comorbidities, TICI score, and NIHSS[55].

Clinical implications

The findings of this meta-analysis have important implications for clinical practice. Given the observed association between anemia and worse functional outcomes and increased mortality, routine assessment of hemoglobin levels should be considered an integral component of risk stratification in patients undergoing mechanical thrombectomy. Identification of anemia on admission or in the early post-procedural period may help clinicians recognize patients at higher risk of unfavorable outcomes. Although current stroke guidelines do not provide specific recommendations regarding anemia management in this population, our results suggest that optimizing hemoglobin levels may represent a potentially modifiable factor to improve recovery. Careful consideration of peri-procedural blood loss, minimization of unnecessary aspiration, and individualized evaluation of anemia correction strategies may contribute to improved post-thrombectomy outcomes.

Strengths and limitations

This meta-analysis offers a thorough assessment of anemia’s effect on mechanical thrombectomy outcomes in ischemic stroke patients, consolidating data from many retrospective cohort studies across different geographical areas. The incorporation of 2189 cases enhances the statistical robustness of the results. The analysis evaluates several critical outcome indicators, such as functional recovery, mortality, and predictive factors, providing a comprehensive view of the correlation between hemoglobin levels and stroke prognosis. The stringent technique, incorporating PRISMA-guided research selection and quality evaluation, bolsters the credibility of the findings. Moreover, recognizing predictive markers like age, initial NIHSS and hemoglobin levels offers significant therapeutic insights for patient risk classification and management. This meta-analysis, notwithstanding its virtues, possesses significant drawbacks. Initially, all studies included were retrospective, potentially introducing selection bias and constraining the capacity to prove causality. A further drawback is the absence of data regarding confounding variables, including comorbidities, nutritional status, and transfusion practices, which may affect both anemia and stroke outcomes. Finally, the limited sample sizes in certain studies may diminish the generalizability of the results.

Recommendations for future practice

Future research ought to concentrate on prospective, multicenter trials to elucidate a more definitive causal association between anemia and stroke outcomes post-mechanical thrombectomy. Additional examination of the effects of anemia correction methods, such as blood transfusions and iron supplementation, on post-thrombectomy results is necessary. Furthermore, investigations into the molecular processes connecting anemia to suboptimal neurological recovery may aid in identifying prospective treatment targets. The findings indicate that monitoring and optimizing hemoglobin levels in stroke patients receiving thrombectomy may be advantageous. Personalized patient treatment techniques must regard anemia as a controllable risk factor throughout both the acute and post-recovery stages of stroke therapy.

Conclusion

This meta-analysis demonstrates that anemia is associated with poorer functional outcomes and increased mortality in ischemic stroke patients undergoing mechanical thrombectomy. Higher hemoglobin levels, younger age, and lower baseline NIHSS scores were identified as significant predictors of better neurological recovery. These findings underscore the importance of evaluating hemoglobin concentrations as part of stroke management and highlight the need for further research on targeted interventions to optimize hemoglobin levels in this patient population. Addressing anemia may represent a potential avenue for improving stroke recovery and long-term outcomes following mechanical thrombectomy.

Footnotes

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Supplemental Digital Content is available for this article. Direct URL citations are provided in the HTML and PDF versions of this article on the journal's website, www.lww.com/annals-of-medicine-and-surgery.

Published online 15 April 2026

Ethical approval

Ethics approval was not required.

Consent

Informed consent was not required.

Sources of funding

This research received no external funding.

Author contributions

M.H.E.D.M.: Conceptualization and methodology. M.H.E.D.M., I.S., A.F.G., and M.K.M.: Investigation and data curation. I.S.: Formal analysis. M.H.E.D.M., I.S., I.M.A., H.A.A.: Writing – original draft. M.A.: Supervision. I.S.: Project administration. M.A.: Writing – review and editing. All authors read and approved the final content.

Conflicts of interest disclosure

The authors have no conflicts of interest to declare.

Research registration unique identifying number (UIN)

Not applicable.

Guarantor

Hamza A. Abdul-Hafez.

Provenance and peer review

Not commissioned, externally peer-reviewed.

Data availability statement

All data generated or analyzed during this study are included in this published article.

Declarations

This work is compliant with the TITAN Guidelines 2025[56].

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Data Availability Statement

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